| Home | Dolphin Store | Online Reservation | TropicalAdventure.com |
|
|
DolphinWorld.org Newsletter | |||
|
|
| Staying close to mother helps baby dolphins swim - but they can't keep together when fleeing from fishing boats. Why has the introduction of dolphin-friendly tuna-fishing methods not led to a recovery of dolphin populations? A new study shows how chase by tuna fishermen may sever the link between mother and baby dolphins, to disastrous effect. Young dolphins keep up with their mothers, who are more powerful swimmers, by adopting the ideal position to get a 'free ride' in the mother's slipstream, according to an article published this week in the top-tier Open Access journal, Journal of Biology. Fleeing from fishing boats is likely to disrupt the positioning of mother-calf dolphin pairs, causing the younger dolphins to get permanently separated from their mothers. Daniel Weihs, an aerospace engineer at Technion, the Israel Institute of Technology, has modeled the complex hydrodynamic interactions between two dolphin-shaped objects traveling through water. He wanted to understand the phenomenon known as 'drafting' whereby dolphin calves position themselves close to their mothers' side in an apparent attempt to reduce the forces required for swimming.
The first is similar to the slipstream effect that is well known to racing cyclists, while the second (the Bernoulli effect, which also causes aircraft to stay aloft) tends to pull the calf sideways, in towards its mother's flank. If the calf and the mother are side-by-side and almost touching, the movement of these two effects means that the calf can almost get an energetically free ride, relying on its mother's swimming efforts to carry it along. In the ideal position the mother can provide close to 90% of the thrust needed for the young cetacean to move at around 8.5 km per hour. The author writes: "The maximum thrust is provided when the calf's center of mass is approximately at 2/3 of the mother's length. This position does not change as the calf grows, which is probably very useful as the calf has to learn only one such position." Analysis of aerial photographs of eastern spinner dolphins show that calves do indeed tend to adopt the position predicted to be the most energy-efficient for forward travel by Weihs' model. The drafting situation in the wild is much more complex than the simplest model suggests, however, so Weihs examined several additional scenarios, such as what happens when the dolphins move apart or propel themselves along by flapping their tails. He found that as a pair separate the positive forces on the baby dolphin decrease rapidly, and as the dolphins swim faster the relative energy savings that the calf can make are reduced. Weihs suggests, "chases by fishing vessels can easily cause the loss of the mother-calf connection," as the dolphin pair have to move apart when they accelerate to avoid hurting each other as they increase their body movements. Weihs' findings could help explain why the dolphin population of the Eastern tropical Pacific Ocean has not recovered, despite recent restrictions on purse-seine tuna fishing. Fishing that took place prior the restrictions may well have disrupted dolphin schools, causing many younger dolphins to die before they were able to breed. They should also help in evaluating the proposed relaxation of the 'Dolphin-Safe' definition. This relaxation would allow fishermen to set their nets around dolphin schools to catch the tuna living alongside, so long as no dolphins were killed or seriously injured. Weihsís results suggest that relying on fishermen's observations of injuries to dolphins would underestimate the damage inflicted on dolphin populations.
CHILDREN
GET SPLASH OF DOLPHIN THERAPY Robbie has cerebral palsy, which has caused semi-paralysis in his right side. He has other issues from brain damage that he suffered at birth, including memory and learning problems. Marcus credits Robbie's newfound enthusiasm to the time he spent in a dolphin therapy program in the Florida Keys. Island Dolphin Care in Key Largo serves more than 1,000 children each year. The program is filled with children with physical and mental health problems. Patients with terminal cancer, diabetes, immune deficiency disorders, cardiac problems, and autism participate. ''A lot of neurological and brain damage issues are very similar to issues with autistic children and people with attention deficit hyperactivity disorder," Marcus said. These problems can lead to low self-esteem,
depression, and behavioral problems in the children, he said. With a background in education and clinical social work, Hoagland struggled to find something that would help her son after moving to the Florida Keys from Palm Beach in 1990. ''I saw an ad for a Dolphins facility in a local paper that offered a discount to locals," she said of the for-profit profit program that operates from the same facility. ''I called thinking that maybe I could get Joe in the water and maybe that would help him." The owner said to come over sometime; Hoagland showed up that very day. She took a bucket of bait to a dock where the dolphins are confined in a canal, and a dolphin named Fonzie came right up to Hoagland and her son. ''Joe giggled for the first time in months," she said. ''I started bawling like a baby." Hoagland thought this type of experience would help other children with disabilities. Soon after, she founded Island Dolphin Care, and her part-time venture turned into a full-time job in 1996. And while Hoagland cannot heal the children's bodies, she said the program helps heal their spirits. ''The greatest gift is an increase in self-esteem," she said. A child's entire family becomes involved during the five-day sessions, and nearly 300 children participate in classroom and water sessions from March to November. The Marcus family attended that program in March. Paul Marcus said Robbie's doctors encourage them to try ''anything that can improve how the kids feel about themselves." ''How they are able to deal with their own issues will dramatically improve how they feel about themselves," he said. Robbie also rides horses a couple of times a week, and Marcus said that has made ''a dramatic improvement in his life." He said such activities as horseback riding and the dolphin program combine physical therapy with learning and exercises that build self-esteem. Classroom work includes learning about dolphins and their environment as well as art projects. While in the water for the dolphin program, Robbie had to balance himself and work muscles that he would have exercised in a regular physical therapy session. Hanging out in the water with a dolphin was a big plus. ''My son was totally drained at the end of the day," Marcus said. ''He did many hard things for a kid with muscular issues." Marcus thinks the animals and the children share a connection. ''It has an impact that isn't quantifiable yet," he said. ''I don't know that we will know about those things for a long while." These activities are not inexpensive; the five-day session at Dolphin Island Care cost $2,200, Marcus said. But as president of the Davis Companies, a commercial real estate development firm, Marcus said he can and will do anything to help his son. He also raises money to provide scholarships for children whose families cannot afford to pay. Marcus also serves on the board of trustees of Boston Children's Hospital and is founder of the Philanthropic Leadership Council for the Developmental Medicine Center at Children's Hospital. And he is on the visiting committee of MIT's Brain and Cognitive Science Center. Hoagland said she is committed to running the program as long as the dolphins are in good health. She has permits for the three captive dolphins, which cannot live in the wild, and has committed to lifetime care. Bahamas Wild Dolphin Vacations
Last
Change for Summer Reservations!!
Get A FREE 8"X10"
Dolphin Photo Link Placement Instructions // TOP \\ TropicalAdventure.com Kayaking in Cocoa Beach. You might see Manatees!! Win FREE Dolphin Swims Plus Snorkel Trip, Sunset Cruise Plus More From TropicalAdventure.com!
// TOP
\\ Click
Here during the day to see some incredible
LIVE Dolphin images (Go!) |
FREE Dolphin World Calendar
|
||||||||||||||||||||||||||||||||
| ©2002 DolphinWorld.org | Unsubscribe
By Email • Unsubscribe
By Website • Did you receive your free gift of eternal life? Click
Here.  |
